It is known that metallic silver can be an effective bactericide for treating water. For this purpose U.S. Pat. No. 2,434,190 describes the preparation of a "silvered" anion exchange resin. As described in this patent, the anion exchange resin in the sodium form may be treated with a solution of silver nitrate to load the resin with silver ions. The resin is next treated with a reducing agent such as potassium metabisulfite to form metallic silver. It is stated that the silvered resin can be used for disinfecting water.
U.S. Pat. No. 2,692,855 discloses using a cation exchange resin in a silver ion form for disinfection of water. As described in the patent, for example, a cation exchange resin in the hydrogen form may be treated with a solution of a silver salt to exchange silver ions for hydrogen ions, thereby producing a resin for disinfecting water. However, the presence of silver ions in drinking water can be a health hazard, and drinking water contains metal ions that will exchange with the silver ions on the resin. To minimize release of silver ions into the solution being treated, the water can first be demineralized by passing it through an cation exchange resin in the hydrogen form to remove metal cations.
Cation exchangers, such as zeolite and synthetic cation exchange resins, have been reacted with solutions of silver salts to exchange the silver ion for the hydrogen or alkali metal cations of the exchangers. Such silver ion-containing resins have been used to remove halides from water, such as the removal of chloride ions from sea water. See U.S. Pat. No. 3,382,039, United Kingdom Patent 576,969 and Australian Patent 122,647. Silver ion-containing cation exchange resins have also been proposed for use in removing iodine and methyl iodide from waste streams, and removing halides from liquid carboxylic acid (U.S. Pat. No. 5,139,981). In such applications, the release of silver ions into the solution being processed may not be as objectionable as with potable water.